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U.S. military personnel observe the 15th anniversary of the September 11, 2001 attacks at the... [+] International Security Assistance Force (ISAF) headquarters in Kabul on September 11, 2016. (WAKIL KOHSAR/AFP/Getty Images)

The national debt is $19.7 trillion and climbing fast. Oft ignored in favor of the comparatively small federal deficit (only when considering such trillions can $590 billion sound “small”), the debt has been thrown back into the limelight by election season, as each candidate promised to have the perfect combination of fiscal policies to get our books in order.

What’s often missing from such calculations and debt conversations more broadly is the foreign policy outlook—or, perhaps I should say, our obscene indebtedness is left out of foreign policy debates. Either way, the massive fiscal ramifications of the past decade and a half of interventionism seem to have had no effect on Washington, as politicians complain about the debt in one breath and then blithely propose massive new military entanglements in the next.

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But after the last 15 years, the literal costs of war should not be a difficult lesson to learn. A report from Brown University last month calculated the long-term price of the wars in Iraq and Afghanistan (including interest payments and healthcare commitments to veterans) would top $12 trillion by 2053 if both wars are completely finished by the end of 2017, at this rate an implausible prospect. Already these two conflicts—hardly the totality of our present interventions—are responsible for a good $5 trillion of that $19.7 trillion sum.

And that’s just the money that was supposed to be spent. As it happens, the Pentagon is unique among federal agencies in having never undergone a full audit, an oversight with serious national security consequences. While some on the right treat the Pentagon as an honorary member of the private sector, it is, in fact, a federal agency,—and experience suggests it accordingly has outdated programs, misallocated expenditures, and even simple waste that ought to be addressed (sans audit, an impossible task).

The good news is Congress has finally mandated an audit be completed by September of 2017, a deadline reached after the Department of Defense managed to skirt a government-wide audit requirement for more than two decades. The bad news is likely the audit results themselves.

After all, a recent audit of the Army General Fund found bookkeepers somehow screwed up their accounting by $6.5 trillion in 2015. That number is particularly remarkable given that it is 13 times the size of the entire Pentagon budget for that year. “How could the Army misplace, fudge, misappropriate or otherwise lose $6.5 trillion?” asked an incredulous Matthew Gault reporting on the Army audit for War Is Boring. “It’s simple. Years of no oversight, bad accounting practices and crappy computer systems created this problem. And remember, this is just the Army and just its general fund.”

If that’s the sort of rot we find in a single branch of the military, imagine the fiscal horrors yet to be uncovered throughout.

On top of these direct costs, an imprudent interventionist foreign policy provides an easy excuse for fuzzy math and escalated domestic spending, too. Each year, when it comes time to make a budget (or, in recent years, to pass some rushed, ramshackle monster of a bill to avert government shutdown), we see the same deceptive dance play out: War funding is used as cover to grow non-war expenditures that can’t be fit into the Pentagon’s base budget while remaining in technical compliance with spending caps. It’s a sketchy workaround that allows Congress to spend more money it does not have.

Meanwhile, congressional deal-making to approve higher military expenditures—which, again, flow to an unaudited agency where waste and fiscal misconduct is almost certainly occurring on a habitual basis and massive scale—typically takes the form of a compromise in which more defense dollars are bought at the price of more domestic outlays. This de facto system of perverse incentives has led to many a “fiscal conservative” caving to massive across-the-board spending hikes. And thus each side gets the spending it wants; the Pentagon can throw more money into its abyss; and the national debt ticks up, up, up.

The loser in all this is the American taxpayer. Not only are we asked to finance unconstitutional, aimless and apparently endless wars, but we’re asked to put them on our children and grandchildren’s tab. Joint Chiefs of Staff Chairman Adm. Michael Mullen famously argued the national debt itself is the “most significant threat to our national security.” Let it continue to grow unabated, he says, and we risk being unable to maintain an adequate defense budget.

Mullen is concerned about long-term consequences, but there are short-term risks, too. To wit, war feeds the debt on an enormous and yet generally ignored scale, while an endless supply of borrowed money makes it easier to launch unnecessary and even counterproductive interventions without the strategic calculations such commitments should require.

We can no longer fail to account for our fiscal constraints when developing our foreign policy; and we can no longer accept politicians’ misleading debt reduction proposals that ignore their authors’ own plans for more reckless, expensive intervention. Interventionism and debt have gone hand in hand for the better part of two decades. If we are serious about getting a handle on the $19.7 trillion debt, it is past time we call out that connection.